Question: Which of these numbers is prime? ${12,\ 25,\ 29,\ 65,\ 75}$
A prime number has exactly two factors: 1 and itself. The factors of 12 are 1, 2, 3, 4, 6, and 12. The factors of 25 are 1, 5, and 25. The factors of 29 are 1 and 29. The factors of 65 are 1, 5, 13, and 65. The factors of 75 are 1, 3, 5, 15, 25, and 75. Thus, 29 is a prime number.